Isoeugenol
Eugenol's spicier cousin — a Fragrance Mix I member and one of the stronger fragrance sensitisers
INCIIsoeugenol
- Category
- Fragrance
- Risk level
- medium
- Why it's flagged
- EU-labelled fragrance allergen; a comparatively strong Fragrance Mix I sensitiser
- What it is
- A structural isomer of eugenol from clove, ylang-ylang, nutmeg, and cinnamon bark
- Relative risk
- Among the more potent fragrance sensitisers — generally stronger than eugenol itself
- Cross-reactors
- Eugenol (co-sensitisation is common); related clove/balsam materials
- EU labelling
- Must be named above 0.001% (leave-on) / 0.01% (rinse-off); on the expanded 2023 allergen list
Look for these names on ingredient lists
This ingredient may appear under any of these names:
Commonly found in
Possible reactions
- Allergic contact dermatitis
- Facial rash from perfumed cosmetics
- Perioral dermatitis from clove-containing dental products
- Cross-reactions with eugenol
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What is isoeugenol?
Isoeugenol (INCI: Isoeugenol) is a clove-and-carnation-scented fragrance compound found naturally in clove oil, ylang-ylang oil, nutmeg, and cinnamon bark. It's the structural isomer of eugenol — the two differ only in the position of a double bond — and perfumers use it for warm, spicy, carnation-like notes in floral and oriental compositions.
It's one of the eight components of Fragrance Mix I (FM I), the primary fragrance-allergy patch-test screen, and an EU-labelled allergen.
Why it's one of the stronger sensitisers
Isoeugenol is a moderately strong-to-potent sensitiser — generally stronger than eugenol itself. Its allergenicity involves oxidative activation: in the skin, isoeugenol can be converted to reactive intermediates (quinone methides and epoxides) that bind proteins covalently, forming the haptens that drive Type IV contact allergy.
The defining clinical feature is its tight relationship with eugenol: co-sensitisation and cross-reactivity are common, so finding one usually means avoiding both — and the broader clove/balsam family. As with eugenol, dental and oral exposure (clove-containing materials and remedies) can produce perioral and oral mucosal reactions.
Isoeugenol's biggest modern blind spot is "clean"/aromatherapy products. Ylang-ylang and clove oils are natural sources, so a botanical floral product can carry a relatively strong allergen without ever printing "isoeugenol" on the front. Treat ylang-ylang, clove, and nutmeg oils as likely sources if you're sensitised.
How to spot and avoid it
- Read labels for Isoeugenol, and for Ylang Ylang (Cananga Odorata) Oil, Clove (Syzygium Aromaticum) Oil, and Nutmeg (Myristica Fragrans) Oil.
- Avoid clove/spicy and ylang-ylang-forward fragrances if sensitised.
- Treat eugenol as off-limits too — they cross-react.
- Tell your dentist to use clove-free (eugenol/isoeugenol-free) materials.
Safer alternatives
- Fragrance-free personal care for leave-on products.
- Clove-free, fragrance-free hair oils and body care.
- Eugenol/isoeugenol-free (non-clove) dental products.
The bottom line
Isoeugenol is eugenol's spicier, generally stronger sibling — a Fragrance Mix I allergen that travels with clove and ylang-ylang, natural or synthetic. If you react to either clove compound, avoid both and the whole clove/balsam family, and keep it in mind for lip and dental exposures.
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References & further reading
- Eugenol and isoeugenol contact allergy — overview DermNet
- Isoeugenol contact allergy — review PubMed / Contact Dermatitis
- CosIng / Regulation (EU) 2023/1545 (labelled fragrance allergens) EUR-Lex